Understanding On-Site Acoustic Testing: How to Measure Real-World Performance

On-site acoustic testing looks at the performance of the completed space rather than the glass wall in isolation. This makes it useful for understanding how the wall, door and adjoining construction are working together in practice.

Setting the acoustic requirement

The required level of sound isolation will depend on how the spaces are being used and the degree of privacy needed between them.

For workplace projects, acoustic requirements may be established by the project specification or an acoustic consultant. Standards such as the WELL Building Standard can also inform the level of sound isolation required between different types of spaces.

The appropriate target therefore depends on factors such as:

• The use of each space
• The level of speech privacy required
• Background noise within the receiving space
• The wall and door configuration

What does an on-site test measure?

Unlike a laboratory test, an on-site measurement includes the effect of the surrounding building.

Sound may travel directly through the glass wall, but it can also bypass it through other routes, known as flanking paths. These can include:

• Ceiling and floor voids
• Building façades and mullions
• Hollow wall or column interfaces
• Mechanical and electrical penetrations
• Gaps around doors and adjoining construction

This means the result represents the sound isolation between the completed rooms, rather than simply repeating the laboratory STC rating of the wall system.

Why can on-site performance differ from STC?

An STC rating is established under controlled laboratory conditions where other sound paths are minimized.

On site, the glass wall becomes part of a much larger construction. If sound can travel through the ceiling, floor, façade, services or door, the measured room-to-room performance may be lower than the laboratory value of the wall itself.

This does not necessarily mean the glass wall is underperforming. It may indicate that sound is bypassing the wall through adjoining elements.

The door matters too

Where a glass wall includes a door, the field result reflects the combined performance of both the wall and door.

A high-performing wall paired with a lower-rated door will therefore not deliver the wall's laboratory STC rating across the complete room front. The size of the door relative to the wall and the effectiveness of its perimeter seals can both influence the overall result.

What should specifiers look for?

For meaningful on-site acoustic performance, the glass wall should be considered as part of the complete room enclosure.

That means coordinating:

• The wall and glass specification
• Door performance and seals
• Ceiling and floor interfaces
• Façade junctions
• Service penetrations
• Acoustic barriers within voids
• Installation detailing

On-site testing can then provide a useful measure of the sound isolation achieved between completed spaces and help identify where additional acoustic treatment may be required.

From laboratory evidence to finished space

Laboratory STC ratings remain important because they allow glass wall systems to be compared under consistent conditions. On-site testing answers a different question: how well does the completed space perform once the wall is integrated into the building?

Understanding that distinction helps project teams set realistic acoustic targets, interpret test results correctly and address the parts of the construction that have the greatest influence on room-to-room sound isolation.